msm: board-msm7x30: Voltage level fix for shared Voltage Regulator.

Some voltage regulators are shared among more than one peripheral
and these peripheral may use different voltage levels. Hence while
setting the voltage levels for such regulators, range of min/max
voltage should be given.

After that voltage regulator framework will choose the appropriate
voltage levels which will meet the constraints for all involved
peripherals. In 7x30 BT & Wifi uses the same regulator.

Change-Id: Ibabfd2e2c946c1b5baac47e087820d641e401968
Signed-off-by: Pankaj Kumar <pakuma@codeaurora.org>